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In the world of virtualization and hypervisors, VMware has been and still remains the top dog in the virtual food chain. But in the open source community, Xen has been the de facto standard for hypervisor technology for quite some time.

But that de facto standard label may be waning for some in the open source community and evaporating into the cloud. Case in point: Red Hat, a longtime supporter of Xen, is giving the virtualization platform the cold shoulder. With its planned release of Red Hat Enterprise Linux (RHEL) 6.0, Red Hat is now ready to officially pull the plug on Xen in favor of the Kernel-based Virtual Machine (KVM) technology developed by Qumranet, which Red Hat acquired back in 2008.

Xen and KVM have co-existed as virtualization platforms within RHEL 5.4 and 5.5, but it should have been clear back then to most that Xen would eventually disappear from the Red Hat distro. Its removal was just a matter of time until the KVM platform and its toolset matured to the point where Red Hat could support its user base on the new technology. According to Red Hat, dropping Xen from the distro will free the company from the large amount of work involved with maintaining two hypervisor code bases.

"Looking to the future, Red Hat Enterprise Linux 6 blurs the lines between virtual, physical, and cloud computing to address shifts taking place in the modern IT environment. Featuring updated core technology, from the kernel to the application infrastructure to the development tool chain, Red Hat Enterprise Linux 6 is designed to meet the needs of the coming generations of hardware and software technologies," said Red Hat in a corporate announcement.

RHEL 6 builds on the integrated KVM-based virtualization provided by earlier releases. It will offer improved flexibility and control, and incorporates numerous performance, scheduler, and hardware support enhancements and features such as sVirt, which protects the guest and host from unauthorized access; SR-IOV and NPIV, which delivers high-performance virtual use of physical devices; and libvirt, which leverages kernel resource management functionality.

But perhaps this latest announcement really shouldn't have been as earth-shattering as some have made it out to be. Some of the "ooh"s and "aah"s may be less about Red Hat dropping Xen from its distro and more about the KVM technology gaining traction, especially within cloud hosting companies. In the past couple of months, hosting providers such as IBM, NTT Communications, and Houston-based The Planet have all said they will begin offering services based on KVM over Xen.

But Xen isn't waiting around for Red Hat support or sitting idly by either. Xen 4.0 was announced last month with more than two dozen new features and improvements that make virtualization more suitable for all types of workloads. And many of the largest and oldest cloud providers are continuing to operate on the Xen hypervisor platform, including companies like Amazon, GoGrid, and Rackspace. That doesn't sound like a community that's going away any time soon.

Still, for me there are other questions that come to mind. What plans or tools does Red Hat have to migrate existing RHEL Xen users over to KVM in order to make the transition a smooth one? Who is the big winner in this announcement, Red Hat or KVM? Numerous folks have mentioned using KVM but are doing so with other Linux distros, like Canonical Ubuntu (and Novell plans to offer KVM in addition to Xen in their coming Suse distro as well).

And finally, with so much attention being given to KVM in the cloud, the cloud seems to be taking the approach of applications operated across a virtualized platform rather than an OS-centric approach to virtualization. How does that affect Red Hat's plans -- or does it? With virtualization companies changing focus, like VMware with its SpringSource acquisition and VMforce news and Oracle's announcement of its WebLogic tools, going after server sockets may be yesterday's battle. Where is Red Hat planning to plant its flag?